Metal-supported porous carbon film, fuel cell electrode and fuel cell employing the electrode

Abstract

A metal-supported porous carbon film wherein metal fine particles with a mean particle diameter of 0.7-20 nm are dispersed and supported on pore surface walls, fuel cell electrodes employing the metal-supported porous carbon film, a membrane-electrode assembly comprising the fuel cell electrodes bonded on both sides of a polymer electrolyte film, and a fuel cell comprising the fuel cell electrode as a constituent element. The support structure is such that metal fine particles having a controlled particle size are uniformly supported to allow effective utilization of the metal-based catalyst, and the fabrication steps are simple.

Description

TECHNICAL FIELD[0001]The present invention relates to a metal-supported porous carbon film, to a fuel cell electrode and to a fuel cell employing the electrode.BACKGROUND ART[0002]Great advances have been achieved in the development and the implementation of fuel cells, in recent years. In the case of a solid polymer electrolyte fuel cell, for example, the fuel cell is constructed by bonding gas diffusion electrodes obtained by providing a porous carbon film composed of a carbon fiber sheet with a thickness of 0.1-0.3 mm, on the surface of which a platinum-based catalyst is supported as an electrode catalyst on both sides of a polymer solid electrolyte layer, and providing a separator, made of a dense carbon board with a thickness of 1-3 mm and having a gas flow channel on the outside of the porous carbon film, on each side.[0003]In the case of a phosphoric acid-type fuel cell, for example, the fuel cell is constructed by bonding gas diffusion electrodes, obtained by providing a por...

AI Technical Summary

Benefits of technology

The present invention provides a metal-supported porous carbon film that can effectively utilize metal-based catalysts in fuel cells. The support structure consists of metal fine particles uniformly dispersed and supported on the surface of pore walls. This film can be used as a fuel cell electrode, and a membrane-electrode assembly can be easily formed by bonding the electrodes onto a polymer electrolyte film. The fuel cell comprises this electrode as a constituent element. The technical effects of this invention include improved fuel cell performance and simplified fabrication steps.

Problems solved by technology

For application to fuel cell electrodes, however, resin binders with substantially no electron conductivity must be used for molding into film shapes (for example, Japanese Unexamined Patent Publication No. 5-36418), and this has led to such problems as increased internal resistance of the electrodes, poor in-plane uniformity of the reaction and, consequently, inferior battery properties.

However, the important step of stirring in conventional metal dispersing supporting techniques employing metal precursor solutions is difficult to apply to porous carbon films, while it has been extremely difficult to support nanosize-scale metal fine particles in a uniform manner.

Moreover, metals commonly used for fuel cell electrodes, and especially platinum-based materials, are very expensive and, although it is desirable to achieve dispersion and support of fine particles (preferably 2-10 nm fine particles) in a uniform manner in order to maximize their activity per weight, no method has yet been achieved for achieving uniform dispersion while also accomplishing particle size control, and therefore it is currently the case that the supporting of metals, such as platinum, must be accomplished on the basis of experience and intuition.

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